- orEmpty for List and Map.
- firstNotNullOfOrNull for iterable.
- joinToString for iterable.
- fistOrNullIf, lastOrNullIf for List and Iterable.
- Fix mapNotNull issue.
- Fix let issue.
- Add takeUnless.
- Add getOrElse for map.
- Fix mapIndex return -1 issue.
- support mapIndexed and mapNotNull.
- support lastIndex, getOrElse and getOrNull for iterables.
- Initial version.